Flexural strength of palm oil clinker concrete beams

Materials and Design 46 (2013) 270–276

Contents lists available at SciVerse ScienceDirect

Materials and Design

journal homepage: www.elsevier .com/locate /matdes

Technical Report

Shear strength of palm oil clinker concrete beams

Bashar S. Mohammed a,⇑, W.L. Foo b, K.M.A. Hossain c, M. Abdullahi d

a Department of Civil Engineering, Universiti Teknologi Petronas, Bandar Sri Iskandar, 31750 Tronoh, Perak Darul Ridzuan, Malaysiab Civil Engineering Department, College of Engineering, Universiti Tenaga Nasional, Km-7, Jalan Kajang-Puchong, 43009 Kajang, Selangor, Malaysiac Department of Civil Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B 2K3d Department of Civil Engineering, Federal University of Technology, Minna, Nigeria

a r t i c l e i n f o a b s t r a c t

Article history:Received 11 April 2012Accepted 16 October 2012Available online 1 November 2012

0261-3069/$ - see front matter � 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.matdes.2012.10.021

⇑ Corresponding author. Tel.: +60 53687305.E-mail address: [email protected]

This paper presents experimental results on the shear behavior of reinforced concrete beams made ofpalm oil clinker concrete (POCC). Palm oil clinker (POC) is a by-product of palm oil industry and its uti-lization in concrete production not only solves the problem of disposing this solid waste but also helps toconserve natural resources. Seven reinforced POCC beams without shear reinforcement were fabricatedand their shear behavior was tested. POCC has been classified as a lightweight structural concrete withair dry density less than 1850 kg/m3 and a 28-day compressive strength more than 20 MPa. The exper-imental variables which have been considered in this study were the POCC compressive strength, shearspan–depth ratio (a/d) and the ratio of tensile reinforcement (q). The results show that the failure modeof the reinforced POCC beam is similar to that of conventional reinforced concrete beam. In addition, theshear equation of the Canadian Standard Association (CSA) can be used in designing reinforced POCCbeam with q P 1. However, a 0.5 safety factor should be included in the formula for q < 1.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

Increase in population has made large demand on constructionmaterials causing a chronic shortage of building materials andincreasing their cost. To solve this problem, engineers are not onlychallenged for the future homebuilding in terms of controlling theconstruction costs but also to convert the industrial wastes to use-ful construction and building materials. To achieve this purpose,researchers have introduced industrial waste materials into con-crete as aggregate to preserve the natural resources and to find asafe method of depositing these waste materials instead of dump-ing them into the landfills. Examples of these waste materials arewood chipping, paper mill, crumb rubber, palm oil clinker, etc.

Malaysia is one of the world largest producers of palm oil andsignificant amount of waste are generated in the milling process[1,2]. The large amount of waste produced is one of the main con-tributors to the nation’s pollution problem. Palm oil mills in Malay-sia incinerate palm oil waste to produce steam needed for oilprocesses, and the by-product of incineration is palm oil clinker(POC). Instead of dumping the POC to landfills, a better waste man-agement option is to crush POC into desired size (fine and coarseaggregate) and utilize it as aggregate to produce lightweight palmoil clinker concrete (POCC) [3]. The density and the strength of POCfalls within the requirements of the structural lightweight concrete[4,5]. Researches have been carried out to study the mechanical

ll rights reserved.

.my (B.S. Mohammed).

properties of POCC [3,6]. Their main outcome is that the POCChas been classified as a structural lightweight concrete in accor-dance with the requirements of the ASTM:C330 and BS8110 [7].Researcher concluded that the chloride permeability of POCC iscomparable to that of the conventional concrete and confirmedthe viability of POC to be used as aggregate in producing of durablestructural lightweight concrete [8]. The use of lightweight concretebenefits the construction industry by overall saving of 10–20% ofthe total cost and allows smaller size of structural member [9].POCC is still a relatively new construction material and the struc-tural performance of the reinforced POCC beams has not beeninvestigated yet. Generally, concrete is weak in tension with tensilestrength of approximately 10% of its compressive strength [10].The shear behavior of reinforced concrete (RC) beam is complexand difficult to predict [11]. For convenience in RC design, empiri-cal equations have been used in the design codes such as AmericanCode (ACI 318) [12], British Standard (BS8110) [7], Euro Code (EC2)[13] and Canadian Standard (CSA) [14]. Although there is no specialprovisions for computing the shear capacity of lightweight RCbeams in the BS8110 and EC2, the ACI adopt the reduction of theshear capacity of a lightweight concrete member by modifyingthe design equation using any of the two approaches. In the firstapproach, the reduction factor of 0.85 for sand lightweight aggre-gate or 0.75 for fine and coarse lightweight aggregate can beapplied. Alternatively, the square root of the compressive strengthof concrete (

ffiffiffiffif 0c

p) in the design equation can be replaced by fct/6.7

in which fct is the splitting tensile strength of the lightweight con-crete with provision that it does not exceed the original square root

B.S. Mohammed et al. / Materials and Design 46 (2013) 270–276 271

relationship [15]. The CSA also has included a reduction factor forlightweight concrete in the shear equation.

In this research, the shear behavior of reinforced POCC beamwithout shear reinforcement (stirrups) was experimentally inves-tigated. Three parameters were considered: longitudinal steel ratio(q), POCC compressive strength and shear span to depth ratio (a/d).The experimental results were compared with those obtained fromshear design equations from various codes and standards.

2. POC aggregate

The POC used in this study was obtained from local palm oilmill. Fig. 1 show the flow diagram to process POC. It was crushedand sieved to the desired particle sizes. Particles less than 5 mmare considered as fine aggregate and particles in the range of5 mm to 14 mm are considered as coarse aggregate.

The result of sieve analysis is shown in Fig. 2. For fine aggregate,the percentage by mass passing sieves 1.18 mm (No. 16), 300 lm(No. 50), and 150 lm (No. 100) are 50.77%, 15.37% and 10.12%,respectively. For coarse aggregate the percentage by mass passingsieves 19.0 mm (3/4 in), 9.5 mm (3/8 in), and 4.75 mm (No. 4) are

(a) Raw oil palm

(b) Oil palm clinker

(c) Fine oil palm clinker aggregate (d

Fig. 1. The fine and coarse oi

100%, 24.93% and 0%, respectively. These experimental values arein accordance with grading requirements for lightweight aggregatefor structural concrete as per ASTM:C330. The result shows thatPOC aggregate is well graded and suitable for use in concrete work.The pore space of the coarse aggregate will be filled by the fineaggregate and in turn the pore space of the fine aggregate will befilled by cement paste forming a strong concrete matrix. This alsoreduces the void space and lowers paste requirement [16].

Aggregates having dry unit weights of less than 1200 kg/m3 areclassified as lightweight aggregate [17]. Due to the porous nature ofPOC aggregate, low bulk density and high water absorption wereexpected. From Table 1 it can be seen that POC fine and coarseaggregate has a unit weight of 1119 kg/m3 and 781 kg/m3, respec-tively. This is approximately 25% lighter compared to the conven-tional river fine sand [18] and 48% lighter compared to thecrushed granite stone [19]. Consequently, the resulting concretewould be lightweight. This reduces the overall dead load in a struc-ture, with a resultant of significant amount of savings in the totalconstruction cost.

In general, most lightweight aggregate have higher waterabsorption values compared to conventional aggregate. AlthoughPOC has high water absorption, even though higher water

clinker

after crushing

) Coarse oil palm clinker aggregate

l palm clinker aggregate.

Fig. 2. Sieve analysis of fine and coarse oil palm clinker.

Table 1Properties of oil palm clinker.

Properties Fine Coarse

Aggregate size (mm) <5 5–14Bulk density (kg/m3) 1118.86 781.08Specific gravity (SSD) 2.01 1.82Moisture content 0.11 0.07Water absorption (24 h) 26.45 4.35Fineness modulus 3.31 6.75Los angeles abrasion value (%) – 27.09Aggregate impact value (AIV) (%) – 25.36Aggregate crushing value (ACV) (%) – 18.08

Table 2Mix proportion of POCC.

Mixreference

Ratio

Water/cement(w/c)

Fine aggregate/cement (fa/c)

Coarse aggregate/cement (ca/c)

M-1 0.2 0.95 0.31M-2 0.4 0.95 0.31M-3 0.6 0.95 0.31

Table 3Properties of the POCC mixtures.

Mixreference

Air drydensity (kg/m3)

Compressivestrength (MPa)

Splitting tensilestrength (MPa)

Elasticmodulus(GPa)

M-1 1837.8 39.8 2.7 26.8M-2 1830.3 31.5 2.3 16.9M-3 1820.1 20.3 1.8 9.7

272 B.S. Mohammed et al. / Materials and Design 46 (2013) 270–276

absorption were reported for pumice aggregate which have a valueof about 37% [20]. However the high water absorption of POCaggregate can be beneficial to the resulting hardened concrete. Ithas been reported that lightweight concretes with porous aggre-gate (high water absorption) are less sensitive to poor curing ascompared to normal weight concrete especially in the early agesdue to the internal water supply stored in the porous lightweightaggregate [21].

From Table 1, it can be observed that the aggregate impactvalue (AIV) and aggregate crushing value (ACV) of POC aggregateswere higher compared to the conventional crushed stone aggre-gates [18]. More specifically the AIV and ACV were approximately34% and 30%, respectively higher compared to the granite aggre-gate. The higher ACV value for the POC aggregate might be causedby the particle of POC used in this study which is porous andangular.

3. Experimental program

3.1. Materials

For the purpose of the current investigation, POC particles lessthan 5 mm and 5–14 mm size were used as fine and coarse aggre-gate, respectively (Fig. 1). Other materials used in the mixes wereordinary cement and potable water. The properties of the POCare presented in Table 1. The mixture proportioning of POCC wereconducted in accordance with the requirements of ACI Committee211.2-98 [22].

3.2. Mix proportions and properties of hardened POCC

Three mix proportions (POCC) were selected as shown in Table2. The air dry density and hardened properties of the POCC at age of28 days are presented in Table 3.The range of compressive strength

for POCC is between 20.3 N/mm2 and 46.8 N/mm2. It is approxi-mately 60% higher than the minimum required strength of 17 N/mm2 for structural lightweight concrete recommended by ASTM:C330. Lightweight concrete normally have density of less than2000 kg/m3 and the air dry density for POCC ranging between1820.1 kg/m3 and 1837.8 kg/m3 are fall within this limit and it isapproximately 16% lighter than normal concrete (2200 kg/m3)[23]. According to the Canadian Standards (CSA), the lightweightconcrete is a concrete having 28 days compressive strength notless than 20 MPa and an air dry density not exceeding 1850 kg/m3 [14].

3.3. Reinforced concrete beam detail

The beams were designed as under-reinforced beams accordingto the requirements of BS8110 [7]. Seven reinforced POCC beamswere designed and fabricated (without shear reinforcement). Allbeams had rectangular cross-sections of 150 � 300 mm, with a to-tal length of 2600 mm and an effective span of 2400 mm. For allbeams, a clear cover of 30 mm was kept constant. The beamdimensions were also sufficiently large to simulate a real structuralelement. The beams details are shown in Table 4. The yieldstrength (fy), for the tension steel bars was 590 MPa. For the pur-pose of the study, three parameters selected (Table 4) the shearbehavior of the reinforced POCC beams are: tension reinforcement

Table 4Test beam details.

Beamreference

Mixref.

Steel barreinforcementtension

Beam size(b � d)mm

q = 100As/bd (%)

Shear span–depth ratio (a/d)

AD-3 M-2 2Y16 150 � 262 1 3AD-1 M-2 2Y16 150 � 262 1 1WC-1 M-3 2Y16 150 � 262 1 2WC-3 M-1 2Y16 150 � 262 1 2SR-1 M-2 4Y20 150 � 250 3.4 2SR-3 M-2 2Y8 150 � 266 0.3 2AD/WC/

SR-2M-2 2Y16 150 � 262 1 2

B.S. Mohammed et al. / Materials and Design 46 (2013) 270–276 273

ratio (q), shear span to effective depth ratio (a/d) and compressivestrength of the POCC.

3.4. Instrumentation and testing

The strains in both reinforcement and concrete were measuredthrough KYOWA strain gauges. The strain gauge (SG1) model KFG-10-120-C1-11 has been used for tension reinforcing steel and thestrain gauge (SG2) model KFG-5-120-D17-11 has been used forconcrete. All the strains values were recorded using data loggerthroughput the loading history. A small part of the tension barsat the mid-span was ground smooth to facilitate the fixing of thestrain gauges and then silicone gel was used to protect the straingauges for accidental damage during pouring of concrete. The testset up and the instrumentation are shown in Fig. 3. The reinforcedPOCC beams were simply supported and tested under two-pointloading. The load from the hydraulic jack was transferred to thereinforced POCC beam by means of a spreader beam and theapplied load was measured by using a load cell which connectedto data logger. A linear voltage displacement transducer (LVDT)was placed at centre of the beam to measure the deflection. Duringtesting, the beams were preloaded with a minimum force of 0.5 kNto allow initiation of the LVDTs and strain gauges. The load appliedincrementally with 5 kN for each increment and the load was keptconstant for 5 min after each increment to allow the load distributeequally and stably to the beam. All strain, crack width and deflec-tion measurements were recorded at every load increment. Thefirst crack load was recorded immediately after the formationand all the cracks were marked as and when they propagated inthe beam.

4. Result and discussions

4.1. Structural behavior

The experimental results such as the shear cracking load, failureload and failure mode are summarized in Table 5.

Fig. 3. The experimental set-up fo

4.2. Failure mode

For reinforced POCC beam AD-1 (a/d < 2), bending (flexural)cracks did not develop but shear cracks (at approximately 45�)suddenly appeared and run through the compression zone andproduced collapse as shown in Fig. 4. While for the rest of thebeams (6 > a/d > 2), the initial bending cracks were occurred andbecame inclined early in the loading stage (about 15% of the failureload) and at collapse, horizontal cracks were formed and runningalong the line of the tensile reinforcement. These horizontal cracksreduced the shear resistance of the section by destroying the dowelforce and reducing the bond stresses between the steel and POCCas shown in Fig. 5. For all reinforced POCC beams, the longitudinalsteel in the tension zone did not reach the yielding strength. It isworthy of notice that the mode of shear cracking of the reinforcedPOCC beams is similar to that of RC beams made with conventionalconcrete without shear reinforcement [24].

4.3. Concrete and steel strain

Strains versus applied load for tension reinforcement and con-crete are shown in Figs. 6 and 7, respectively. Fig. 6 shows thatthe tension steel did not yield as the maximum strain was lowerthan the yield strain of 0.0025. Fig. 7 shows that the concrete incompression did not reach the full strain capacity value for OPCCwhich is about 0.0038.

4.4. Theoretical shear resistance of reinforced POCC versusexperimental values

The theoretical shear resistance of the reinforced POCC beams(Vc) was calculated using the equations given in the BS 8110 (Eq.(1)–(3)), ACI 318-02 (Eq. (4)), EC 2 (Eq. (5)–(7)) and CSA (Eq. (8))and compared with the experimental results in Table 6.

Vc ¼0:791:25

100As

bwd

� �1=3 400d

� �1=4 fcu

25

� �1=3

bwd ð1Þ

where

100As

bwd� 3 ð2Þ

400d� 1 ð3Þ

Vc ¼kffiffiffiffif 0c

p6

bwd ð4Þ

Vc ¼ CRd;cKð100q1fckÞ1=3h i

bwd > 0:035K3=2f 1=2ck bwd ð5Þ

where

r the reinforced POCC beam.

Table 5Summary of the experimental results.

Beamreference

First shearcrack (kN)

Failureload (kN)

Ultimate shearforce, Vc (kN)

Failuremode

AD-3 23 55 27.5 Shear/anchorage

AD-1 16 39 19.5 Shear/compression

WC-1 13 43 21.5 Shear/anchorage

WC-3 14 50 25 Shear/anchorage

SR-1 14 61 30.5 Shear/anchorage

SR-3 7 25 12.5 Shear/anchorage

AD/WC/SR-2

10 46 23 Shear/anchorage

Fig. 4. Crack patterns and shear-anchorage failure mode of beam AD-1.

Fig. 5. Crack patterns and shear-anchorage failure mode of beam SR-1.

Fig. 6. Reinforcement strains in POCC beams without shear reinforcements.

Fig. 7. Concrete strains in POCC beams without shear reinforcements.

274 B.S. Mohammed et al. / Materials and Design 46 (2013) 270–276

K ¼ 1þffiffiffiffiffiffiffiffiffi200

d

r� 2 ð6Þ

q1 ¼As

bwd� 0:02 ð7Þ

Vc ¼ b/ckffiffiffiffif 0c

qbwd ð8Þ

where As is the ratio of flexural reinforcement which extended be-yond the section considered, bw is the width of the beam, d is theeffective depth of the beam, fck ¼ f 0c is the compressive strength ofPOCC (cylinder), fcu is the compressive strength of POCC(cube) = f 0c=0:8 where 25 � fcu � 40;CRd;c ¼ 0:18

cc; cc , is the partial fac-

tor for concrete = 1.5, /c is the resistance factor of concrete = 0.65, kis the factor for concrete low-density concrete = 0.75, b is factoraccounting for shear resistance of cracked concrete = 0.18.

By comparing the Codes prediction of shear force (Table 6)against the experimental results, the following observations canbe made: except the CSA, all shear formulas for the other Codes(BS8110, ACI and EC2) have overestimated the shear capacity ofthe reinforced POCC beam. Therefore, it is unsafe for design engi-neers to use these Codes in predicting shear capacity of reinforcedPOCC beam. On the other hand, shear formula based on the CSAunderestimated the shear capacity of the reinforced POCC beam(except for lower q). Therefore CSA based equation can be usedin predicting the shear capacity of reinforced POCC beam havingq P 1 with adequate safety. While, a safety factor of 0.5 shouldbe included in CAS Eq. (8) for POCC beams with q < 1.

4.5. Effects of the study parameters on the shear force of reinforcedPOCC beams

Failure load versus longitudinal steel ratio for the reinforcedPOCC is shown in Fig. 8. The failure load increases as the longitudi-nal steel ration increases. This is due to the fact that the increase inthe steel ratio increases the zone of influence (dowel force) of steelin reinforced concrete beam and subsequently increases the failure

Table 6Comparison of experimental and predicted results for reinforced POCC beams.

Beamreference

Experimental shear force (Vexp)(kN)

Vc (BS8110)(kN)

Vc (ACI)(kN)

Vc (EC2)(kN)

Vc (CSA)(kN)

Vc exp/Vc

BS8110Vc exp/Vc

ACIVc exp/Vc

EC2Vc exp/Vc

CSA

AD-3 27.5 32.1 27.6 27.8 19.3 0.86 0.99 0.99 1.42AD-1 19.5 32.1 27.6 27.8 19.3 0.61 0.71 0.70 1.01WC-1 21.5 27.7 22.1 24.1 15.52 0.78 0.97 0.89 1.39WC-3 25 32.2 40 30.2 21.7 0.78 0.63 0.83 1.15SR-1 30.5 44.5 26.3 34 18.5 0.69 1.16 0.90 1.65SR-3 12.5 21.4 28 18.9 19.6 0.58 0.45 0.66 0.64AD/WC/SR-2 23 32.1 27.6 27.8 19.3 0.72 0.83 0.83 1.19

Fig. 8. Ultimate shear force versus longitudinal steel ratio.

Fig. 9. Failure load versus POCC compressive strength.

Fig. 10. Load versus shear span–depth ratio.

B.S. Mohammed et al. / Materials and Design 46 (2013) 270–276 275

load in shear. In reinforced concrete beam made with conventionalconcrete, the contribution of the dowel force between concrete andtension steel to the shear stress is 35–50%. Therefore, the shearforce increases as the ratio of longitudinal reinforcement increases.Fig. 8 shows that the behavior of reinforced POCC beam in shear isin agreement with that of conventional RC beam.

The effect of POCC compressive strength on failure load isshown in Fig. 9. The failure load increases as the POCC compressivestrength increases. The compressive strength of conventionalconcrete contributes 20–40% to the shear stress of the RC beam.Therefore, the failure load of the RC beam increases as the com-pressive strength of the concrete increases. Similar behavior hasbeen shown by reinforced POCC beams as shown in Fig. 9.

Fig. 10 shows the effect of shear span to effective depth ratio (a/d) on failure load of POCC beams. The failure load decreases withthe decease of a/d. There are four types of failure of reinforced con-crete beam without shear reinforcement depending a/d. They are:(1) a/d > 6; the mode of failure is similar to that of pure bending,(2) 6 > a/d > 2; the mode failure is in shear due to the anchorage

failure between tensile steel and concrete, (3) a/d < 2; the modefailure is in shear due to the failure in compression zone and (4)a/d = 0; punching shear failure will occur [24]. Therefore, failuremode of the reinforced POCC beams with respect to a/d is in goodagreement with that of the normal reinforced concrete beam.

5. Conclusions

Experimental results of shear behavior of reinforced lightweightpalm oil clinker concrete (POCC) beams without shear (web) rein-forcement are presented. The results from this study have shownthat the shear behavior of reinforced POCC beam is comparableto conventional reinforced concrete beam. On the basis of the re-sults obtained in this study, the palm oil clinker (POC) can be usedas lightweight aggregate for the production of structural concreteas per requirements of ASTM:C330. In addition, the POCC can beclassified as lightweight concrete for structural use as per require-ments of the ASTM:C330 and CSA23.3. The structural behavior andfailure mode of the reinforced POCC beam under shear are similarto that of reinforced conventional concrete beam. It is worthy ofnote that the CSA based design equation can be used for the predic-tion of shear capacity of POCC beams with reinforcement ratioq P 1 with adequate safety. However, a safety factor of 0.5 shouldbe included in the CSA formula for POCC beams with q < 1.

References

[1] Mannan MA, Ganapathy C. Concrete from an agricultural waste–oil palm shell(OPS). Build Environ 2004;39:441–8.

[2] Mannan MA, Ganapathy C. Engineering properties of concrete with oil palmshell as coarse aggregate. Constr Build Mater 2002;16:29–34.

[3] Mohammed BS, Al-Ganad MA, Abdullahi M. Analytical and experimentalstudies on composite slabs utilising palm oil clinker concrete. Constr BuildMater 2011;25:3550–60.

[4] Neville AM. Properties of concrete. 4th ed. Pitman Book Limited; 1995.[5] Mindess S, Young JF, Darwin D. Concrete. 2nd ed. Prentice Hall; 2002.

276 B.S. Mohammed et al. / Materials and Design 46 (2013) 270–276

[6] Ahmad MH, Mohd S. Mechanical properties of palm oil clinker concrete. In:Proceedings of 1st engineering conference on energy and environment.Malaysia: Sarawak; 2007.

[7] BS 8110: Part 1: 1997. Structural use of concrete. Part 1. Code of practice fordesign and construction. London: British Standards Institution; 1997.

[8] Mohammed BS, Hossain KMA, Foo WL, Abdullahi M. Rapid chloridepermeability test on lightweight concrete made with oil palm clincker. J EngRes Appl 2011;1:1863–70.

[9] Jumaat MZ, Alengaram UJ, Mahmud H. Shear strength of oil palm shell foamedconcrete beams. Mater Des 2009;30:2227–36.

[10] Kankam CK, Asamoah MA. Shear strength of concrete beams reinforced withsteel bars milled from scrap metals. Mater Des 2006;27:928–34.

[11] Kuo WW, Cheng TJ, Hwang SJ. Force transfer mechanism and shear strength ofreinforced concrete beams. Eng Struct 2010;32:1537–46.

[12] ACI: Part 3. Manual of concrete practice. American Concrete Institute; 2002.[13] Eurocode2. Design of concrete structures. The European Standard; 2004.[14] CSA Standard. Design of concrete structures. Canadian Standards Association;

2004.[15] Kum YJ, Wee TH, Mansur MA. Shear strength of lightweight concrete one-way

slabs. In: Proceedings: our world in concrete and structures: 28, 29 August.Singapore: CI-Premier PTE LTD; 2007.

[16] Mindess S, Young JF, Darwin D. Concrete. 2nd ed. New Jersey, USA: PearsonEducation, Inc.; 2003.

[17] Owens PL. In: Clarke JL, editor. Lightweight aggregates for structural concretestructural lightweight aggregate concrete. London: Blackie Academic &Professional; 1993.

[18] Delsye CL, Manna MA, Kurian JV. Flexural behavior of reinforced lightweightconcrete beams made with oil palm shell (OPS). J Adv Concr Technol2006;4(3):1–10.

[19] Teo DCL, Mannan MA, Kurian VJ. Structural concrete using oil palm shell (OPS)as lightweight aggregate. Turkish J Eng Environ Sci 2006;30:1–7.

[20] Hossain KMA. Properties of volcanic pumice based cement and lightweightconcrete. Cem Concr Res 2004;34(2):283–91.

[21] Al-Khaiat H, Haque MN. Effect of initial curing in early strength and physicalproperties of a lightweight concrete. Cem Concr Res 1998;28(6):859–66.

[22] ACI Committee 211.2. Standard practice for selecting proportion for structurallightweight concrete. Detroit: American Concrete Institute; 1998.

[23] Teo DCL, Mannan MA, Kurian VJ. Structural concrete using oil palm shell (OPS)as lightweight aggregate. Turkish J Eng Environ Sci 2006;30:1–7.

[24] Martin LH, Croxto PCL, Purkiss JA. Concrete design to BS 8110. 1st ed. London,Melbourne, Auckland: Holder Arnold; 1991.